The invention relates to a fluid control valve comprising a cylindrical housing with at least one opening through a housing wall, a cylindrical main valve axially movably arranged inside the housing for controlling a fluid flow through the at least one opening and a main valve spring member acting on the main valve. The invention also relates to a heat exchange system comprising a heat exchange fluid circuit having a heat source, a heat exchanger, a heat exchanger by-pass, a fluid pump and a fluid control valve, as well as a method for adjusting the axial position of a cylindrical main valve of a fluid control valve.
The fluid control valve according to the invention is particularly suitable as flow control valve in heat exchange systems having a heat exchanger device and a bypass line, where the fluid control valve according to the invention is arranged to control the ratio of flow through the heat exchanger device and bypass line. The heat exchange system may be used together with any type of heat source, in particular combustion engines, such as combustion engine for heavy-duty vehicles, such as trucks, buses and construction equipment. Although the invention will be described mainly with respect to a combustion engine for a truck, the invention is not restricted to this particular type of heat source, application or vehicle, but may also be used in heat exchange systems for other heat sources, such as electrical machines, electrical storage systems, hydraulic systems and components, and the like.
There is a continuous effort for reducing fuel consumption of combustion engines. One parameter affecting fuel consumption is the internal resistance within the engine and transmission, and this internal resistance is a function of the viscosity of the lubrication oil within the combustion engine. Low viscosity oil means less resistance but too low viscosity results in reduced lubrication performance, increased wear, reduced lifetime and potential engine damages. Oil viscosity of directly affected be the temperature of the oil, and lubrication oil providers provides detailed information about the maximal allowed oil temperature for a certain lubrication performance. There is consequently a desire by combustion engine providers to control the oil temperature to lie as close as possible to the maximal allowed temperature limit without exceeding said limit. The temperature of the oil within a combustion engine is typically controlled by an oil heat exchange system having oil heat exchanger, an oil heat exchanger bypass, an oil pump and flow control valve. The flow control valve controls the level of flow flowing through the oil heat exchanger and the level of flow flowing through an oil heat exchanger bypass, thereby controlling the overall oil temperature. Conventional fluid control valves for heat exchange system, such as shown in US2013068322, typically rely on a heat element that expands when heated. The heat element, such as wax, is connected to a valve member to actuate the valve position depending on the surrounding heat. This conventional technology for controlling the oil temperature is however not particularly reliable and reacts slowly to changes in incoming oil temperature, Consequently, engine provider are forced to set the oil operating temperature relatively low for the purpose of providing a sufficiently large temperature safety range up to the maximal allowed oil temperature, thereby automatically also operating the engine with an unnecessary high level of internal friction. There is thus a need for a new fluid control valve that reacts faster and that can control the flow with an improved accuracy while maintaining a low cost.
It is desirable to provide a fluid control valve that solves the above-mentioned problem.
The first aspect of the invention concerns a fluid control valve comprising a cylindrical housing with at least one opening through a housing wall, a cylindrical main valve axially movably arranged inside the housing for controlling a fluid flow through the at least one opening and a main valve spring member acting on the main valve. The invention is characterized in that the main valve comprises a base wall defining a fluid control volume and fluid main volume in the cylindrical housing, the base wall comprises an opening for fluidly connecting the fluid control volume with the fluid main volume, and the fluid control valve further comprises:
a pilot valve positioned at the base wall opening, which pilot valve is moveably arranged for controlling a fluid flow through the base wall opening; and an electro-mechanical actuator configured to act on the pilot valve for controlling the main valve via the pilot valve.
It is also desirable to provide a method for adjusting the axial position of a cylindrical main valve of a fluid control valve that solves at least partly the above-mentioned problem.
The fluid control valve comprises a cylindrical housing with at least one opening through a housing wall, and the cylindrical main valve is axially movably arranged inside the housing for controlling a fluid flow through the at least one opening. The inventive method comprises at least one of the steps of                extending an actuator piston of an electro-mechanical actuator in a first axial direction for pushing a pilot valve in an opening direction, thereby enabling increased flow of relatively high-pressure fluid to enter a control volume causing the combined axial forces acting on the cylindrical main valve in the first axial direction to exceed the axial force acting in a direction opposite the first axial direction, such that the cylindrical main valve moves in the first axial direction; and        retracting the actuator piston of an electro-mechanical actuator in a direction opposite the first axial direction for enabling the pilot valve to move in a closing direction, thereby decreasing the fluid pressure within the control volume due to a drain flow out of the control volume, causing the axial force acting on the cylindrical main valve in a direction opposite the first axial direction to exceed the combined axial forces acting in the first axial direction, such that the cylindrical main valve moves in the direction opposite the first axial direction.        
The fluid control valve according to the first aspect of the invention and the method according to the second aspect of the invention solve the above-mention problem by means of the pilot valve that is configured to control the position of the main valve, and controlling the position of the pilot valve by means of the electro-mechanical actuator. The use of an electro-mechanical actuator for controlling the position of the main valve enables a much faster actuation and reaction time compared with a more conventional heat element actuating means. The electro-mechanical actuator is normally controlled by an electronic control unit that receives information about current fluid temperature from one or more sensors. A software control system of the electronic control unit may be used for generating proper control signals to the fluid control valve for maintaining the fluid temperature at a target temperature without excessive deviation. The pilot valve—main valve configuration of the inventive fluid control valve enables high position accuracy of the main valve by use of the fluid pressure as actuating means for controlling the position of the main valve. The electro-mechanical actuator can generally generate a relatively low actuating force, thereby making the actual position of a piston of the actuator uncertain when operating directly on the main valve, due to the relatively high forces acting on the main valve, such as the fluid pressure, main valve spring member and main valve sliding friction. By provision of a pilot valve that controls the position of the main valve by use of the fluid pressure, a more accurate and fast control is provided because much less force is exerted on the pilot valve, thereby making it more easily to control the position of the pilot valve. The position of the pilot valve subsequently controls the flow through the base wall opening, and consequently also the pressure within the fluid control volume, thereby controlling the position of the main valve. The axial position of the piston of the electromechanical actuator may be either estimated based on the control signal transmitted to the electro-mechanical actuator, or measured by a sensing device. The axial position of the main valve can be accurately determined based on the axial position of the piston of the electro-mechanical actuator due to the self-regulating position control of the main valve caused by the axially free floating condition of the main valve in combination with the pilot valve and drain outlet.
According to an embodiment, the cylindrical housing comprises a fluid drain outlet for draining fluid from the control volume. The main force acting on the main valve in a direction towards the fluid control volume is the fluid pressure within the fluid main volume, which fluid pressure is based on the fluid pressure generated by the fluid pump. The main force acting on the main valve in a direction away from the fluid control volume is the fluid pressure within the fluid control volume and the force exerted by the main valve spring member. The fluid drain outlet enables, when connected to a fluid reservoir having a relatively low pressure and with a restricted inflow of high pressure fluid thought the base wall opening, a drain of fluid out from the fluid control volume and thus a reduction in fluid pressure within the fluid control volume. A reduced fluid pressure within the fluid control volume results is an adjustment of the force equilibrium of the main valve, thereby resulting in an adjustment of the axial position of the main valve.
According to an embodiment, the main valve spring member is configured to urge the main valve in a first axial direction away from the fluid control volume. The main valve spring member urging the main valve away from the fluid control volume is an important factor of the force equilibrium of the main valve, and enables displacement of the main valve in the first direction.
According to an embodiment, the pilot valve is moveably arranged for controlling a fluid flow through the base wall opening from the fluid main volume to the fluid control volume. By controlling the position of the pilot valve the level of fluid entering the fluid control volume can be controlled, and thereby also the fluid pressure within the fluid control volume.
According to an embodiment, the electro-mechanical actuator comprises an actuator piston configured such that an axial position of the actuator piston indirectly controls the axial position of the main valve. By controlling the position of the main valve indirectly, the force performance of the actuator may be reduced, thereby enabling use of low-cost actuator.
According to an embodiment, the main valve is configured to be axially free floating, wherein the axial position of the main valve is determined by a force equilibrium position resulting from the accumulated axial forces acting on the main valve. This has the advantage of enabling reduced power performance requirement of the used actuator, such that a more low-cost actuator may be used.
According to an embodiment, the fluid control valve is configured so that the main axial forces acting on the main valve in a first axial direction during operation of the fluid control valve comprises the axial force provided by the main valve spring member and an axial force generated by the fluid pressure in the control volume. This has the advantage of enabling a variable total force in the first axial direction, which total force can be adjusted to a level both lower and higher than the force exerted by the fluid pressure in the fluid main volume.
According to an embodiment, the fluid control valve is configured so that the main axial force acting on the main valve in a direction opposite a first axial direction is the axial force generated by the fluid pressure in the main volume.
According to an embodiment, fluid control valve is configured so that the main axial force or forces acting on the main valve in any single axial direction constitute at least 75% of the total axial forces acting on the main valve in said axial direction, specifically at least 85% of the total axial forces, and more specifically at least 95% of the total axial forces. Additional axial forces may act on the main valve in certain situations, such as frictional forces. These additional forces are however generally relatively low.
According to an embodiment, the pilot valve comprises a circular sealing surface that is configured to sealingly engage a circular surface surrounding the base wall opening. A circular surface may be cost-effective manufactured.
According to an embodiment, the pilot valve during operation of the fluid control valve is configured to be urged towards a closed state by means of a pressure difference between the main volume and control volume. The pressure within the fluid main volume is normally always higher than the pressure within the fluid control volume due to the pressure draining effect of the fluid drain outlet in combination with having the supply of high pressure fluid to the fluid main volume. Consequently, a surge force will be present at the opening in the base wall, which surge force urges the pilot valve towards a closed position. The surge force is generated due to a lower fluid pressure at the control volume side of a sealing flange of the pilot valve than at the main volume side of said sealing flange.
According to an embodiment, the pilot valve comprises an abutment surface configured to interact with an actuator piston of the electro-mechanical actuator, such that the actuator piston can open the pilot valve.
According to an embodiment, the pilot valve comprises a sealing flange and a removable fastener, such as a retaining ring, circlip or the like, and the pilot valve is secured within the base wall opening by means of the sealing flange positioned on the fluid main volume side of the base wall, and by means of the removable fastener positioned on the control volume side of the base wall. The pilot valve needs an arrangement for securing the pilot valve axially slidable within the opening in the base wall. The removable fastener is located on the control volume side of the base wall and arranged to protrude radially beyond the opening in the base wall, thereby forming a stopping member in the first axial direction, and the sealing flange is located on the main volume side of the base wall and protrudes radially beyond the opening in the base wall, thereby forming a stopping member in an axial direction opposite the first axial direction. Assembly of the pilot valve within the opening in the base wall may be performed by first inserting a part of the pilot valve including the sealing flange into the hole of the base wall from the main volume side, and subsequently securing the removable fastener, which may be composed of one, two or more components, to an axial extension of the first part of the pilot valve on the control volume side of the base wall.
According to an embodiment, the pilot valve is secured at the base wall opening by means of cage in which the pilot valve is located, and the cage is fixed with respect to the base wall. The alternative design solution of the pilot valve may omit the removable fastener on the control volume side of the base wall because the pilot valve is secured to the hole in the base wall by the cage instead. The cage, which preferably is installed after the pilot valve was installed in the opening in the base wall, prevents the pilot valve from falling out of the opening in the base wall.
According to an embodiment, the cage comprises a filter for preventing contamination particles within the fluid from entering the control volume. The fluid may contain particles released due to wear of the components in contact with the fluid. These contamination particles may cause malfunction of the fluid control valve, or other parts of the fluid system, and it is desirable to catch and remove these particles from the fluid flow. This can be realised by providing the cage with a filter, such that the fluid entering the fluid control volume is filtered from particles.
According to an embodiment, the pilot valve is preloaded towards a closed position by means of a pilot valve spring member. In case the above-mentioned surge force is considered insufficient or is not available for some reason, the pilot valve may be preloaded towards a closed position by a spring member instead, or in combination with the surge effect.
According to an embodiment, the fluid drain outlet is configured to be connected to a fluid pipe or fluid reservoir that is configured to exhibit a lower fluid pressure than the fluid pressure at a control valve inlet during operation of the fluid control valve, such that the fluid pressure in the control volume is lower than the fluid pressure in the main volume. A lower pressure in the main volume enables motion of the main valve in the direction of the control volume.
According to an embodiment, the control valve comprises a non-variable flow restriction within a fluid drain passage. The fluid drain passage refers to the passage starting at the cylindrical housing and ending at said fluid pipe or fluid reservoir. The flow restriction is preferably provided at the fluid control valve, and may be formed as a throttle. A non-variable flow restriction provides a robust and cost-effective solution.
According to an embodiment, the cylindrical main valve and the cylindrical housing define a piston-cylinder relationship. The term piston-cylinder relationship refers to a relationship with a relatively low leakage and tight tolerances between the parts.
According to an embodiment, the cylindrical main valve comprises a cylindrical sleeve axially movably arranged inside the housing. The cylindrical sleeve ensures coaxial orientation of the main valve and housing.
According to an embodiment, the base wall has a disk-shape and is located within and is attached to the sleeve.
According to an embodiment, the main extension of the base wall defines a plane that is perpendicular an axial direction of the cylindrical housing.
According to an embodiment, the base wall opening is a centrally arranged circular through hole.
According to an embodiment, the electro-mechanical actuator is a linear actuator.
According to an embodiment, the electro-mechanical actuator comprising an actuator piston configured to act on the pilot valve, wherein the actuator piston extends through the fluid control volume.
According to an embodiment, the actuator piston is spring loaded towards a retracted state by means of a spring member. Thereby the actuator may be a single acting actuator, i.e. acting only in one direction.
According to an embodiment, the spring member is provided between an abutment surface of the actuator piston and an opposing abutment surface of the housing.
According to an embodiment, the fluid control volume is delimited by the base wall on one axial side and at least partly by the electro-mechanical actuator on the other axial side. Thereby no passage for the piston through a wall of the housing is required.
According to an embodiment, the fluid control valve is configured for controlling flow of lubrication oil or cooling fluid in a combustion engine. These two fluids have some similarities in terms of requiring a heat exchanging system to dissipate heat from the fluid. The lubrication oil has a cooling fluid effect in a combustion engine, similar to a cooling fluid, such as water cooling fluid.
According to an embodiment, the fluid control valve comprising a fluid inlet, a first fluid outlet and a second fluid outlet, wherein the main valve is configured to control the flow of fluid from the fluid inlet to the first fluid outlet and second fluid outlet respectively as a function of the axial position of the main valve.
According to an embodiment, one of the fluid inlet and outlets are formed by at least a first opening through the cylindrical side wall of the cylindrical housing and another of the fluid inlet and outlets is formed by a second opening through the cylindrical side wall, wherein the first opening being axially displaced from the second opening.
According to an embodiment, the main valve comprising at least one opening through its cylindrical side wall and configured to match at least one of the first and second openings, preferably selectively both of first and second openings, of the housing for controlling the flow of fluid from the fluid inlet to the first fluid outlet and second fluid outlet respectively as a function of the axial position of the main valve.
According to an embodiment, an axial abutment surface of the main valve cooperates with an axial abutment surface of the housing for controlling the flow of fluid from the fluid inlet to the first fluid outlet and second fluid outlet respectively as a function of the axial position of the main valve.
According to an embodiment, a heat exchange system comprising a heat exchange fluid circuit having a heat source, a heat exchanger, a heat exchanger by-pass, a fluid pump and a fluid control valve, wherein the fluid control valve controls the ratio of flow through the heat exchanger and the heat exchanger bypass.
Further advantages and advantageous features of the invention are disclosed in the following description.
The term first axial direction refers to an axial direction of the cylindrical housing that extends from the control volume side of the fluid control valve towards the main volume side of the fluid control valve. This axial direction may alternatively be referred to as main volume direction or direction of the main volume.
The term axial direction opposite the first axial direction refers to an axial direction of the cylindrical housing that extends from the main volume side of the fluid control valve towards the control volume side of the fluid control valve. This axial direction may alternatively be referred to as second axial direction, control volume direction or direction of the control volume.
The term fluid control valve refers to a valve capable of controlling a flow of fluid through the valve.
The term opening through a housing wall refers to any type of opening, though-hole or aperture suitable for forming a flow path thought the opening in the house wall. The opening may enable flow through the opening in an axial direction or radial direction, depending on position of opening.
The cylindrical main valve, which is axially movably arranged inside the housing, is preferably provided with an outer diameter slightly smaller than the inner diameter of the cylindrical housing, such that a relatively low level of leakage is available between the housing and main valve.
The term main valve spring member includes all types of spring members that can exert an axial force, such as helical spring, coil spring, disc spring, compression spring, volute spring, wave spring.
The term base wall refers to wall that divides the cylindrical housing in two axially spaced apart regions. The base wall preferably extends in a plane perpendicular the axial direction of the housing.
The term opening in the base wall refers to any type of opening, though-hole or aperture suitable for forming a flow path thought the opening in the base wall. The opening typically enables flow through the opening in a direction substantially perpendicular to the extension of the base wall. The opening fluidly connects the fluid control volume with the fluid main volume when the pilot valve is in an open position.
The term pilot valve refers to a valve that indirectly controls the axial position of the main valve. The pilot valve has a smaller dimension that the main valve and is therefore more easily actuated that the main valve.
The term electro-mechanical actuator refers to all types of actuators that can mechanically control the position of the pilot valve using electrical energy. A linear electro-mechanical actuator cooperating with an axially displaceable pilot valve is a preferred design due to its relatively non-complexity and low-cost. The invention is however not limited to this design and many alternative designs are possible, such as angular actuators, turning actuators, etc. Furthermore, the actuator as such may be based on solenoid technology, screw thread, or any other technology for generating a mechanical actuation by electrical power.